Generally, electron emission elements are classified, depending upon the kinds of electron sources, into a first type using a hot cathode, and a second type using a cold cathode.
Known among the second type of electron emission elements using a cold cathode are the field emitter array (FEA) type, surface-conduction emission (SCE) type, metal-insulator-metal (MIM) type, and metal-insulator-semiconductor (MIS) type.
The electron emission elements are arranged on a first substrate while forming arrays to make an electron emission device, and the electron emission device is assembled with a second substrate having a light emission unit based on phosphor layers and an anode electrode, thereby constructing an electron emission display.
The FEA-type of electron emission device has electron emission regions, and cathode and gate electrodes as driving electrodes. The FEA-type of electron emission device is based on the principle that when an electric field is applied to the electron emission region under a vacuum atmosphere, electrons are easily emitted from the electron emission region. For this purpose, the electron emission regions are formed with a material having a low work function or a high aspect ratio.
It has been recently studied in the field of the FEA-type of electron emission devices to form the electron emission regions using a carbonaceous material, emitting electrons well even under low voltage conditions.
It is known that carbonaceous materials such as carbon nanotubes, graphite and diamond-like carbon are well adapted for the formation of the electron emission regions. Particularly, the carbon nanotube is spotlighted as an ideal electron emission material as it has an extremely small edge curvature radius of 100 Å, and emits electrons well, even under the application of a low electric field of 1-10V/μm.
Direct growth techniques may be used to form electron emission regions using the carbonaceous material. In order to fabricate an FEA type electron emission device using direct growth techniques, cathode electrodes and a catalytic metal layer are first formed on a substrate. An insulating layer and gate electrodes are then formed on the cathode electrodes and the catalytic metal layer. Openings are formed at the gate electrodes and the insulating layer to expose the catalytic metal layer. A carbonaceous material is grown on the exposed portions of the catalytic metal layer, thereby forming electron emission regions.
However, during the process of growing the carbonaceous material on the catalytic metal layer, carbon remnants may be generated at the unintended area, that is, at the sidewall of the openings of the insulating layer. As the carbon remnants have conductivity, they deteriorate the withstanding voltage characteristics of the cathode and the gate electrodes. In a serious case, the carbon remnants may incur shorts between the cathode and the gate electrodes.
Such problems similarly arise in forming an additional insulating layer and a focusing electrode over the gate electrodes. That is, with the formation of the electron emission regions, the carbon remnants are left at the sidewall of the openings of the additional insulating layer, and deteriorate the withstanding voltage characteristics of the gate and the focusing electrode.
Meanwhile, with the FEA type electron emission device, the cathode electrodes, the catalytic metal layers, the gate electrodes and the focusing electrode are separately formed, each through deposition and patterning, with complicated relevant processing steps.